英文:
GStreamer: how to read mp4 frame by frame and extract capture (camera) time? Need to find closest to given ts frame
问题
给定一些时间戳（可能是秒或毫秒精度），我需要从 mp4 文件中提取与假定的摄像头时间戳（捕获时间，而不是 pts 或 dts）最接近的帧，那么更合适的流程是什么，以提取每个帧在其捕获时间戳内（类似于使用缓冲区中的 GetReferenceTimestampMeta）？考虑到我使用 gstreamer-sharp，我希望使用 appsink 事件，类似于：
private static void AppSink_NewSample(object o, NewSampleArgs args){if (o is AppSink aps){var sample = aps.PullSample();var buf = sample.Buffer;buf.Map(out var info, MapFlags.Read);//application/x-rtpvar tsMeta = buf.GetReferenceTimestampMeta();//NOTE tsMeta 不应为 null...//TODO 一些时间戳比较逻辑buf.Unmap(info);}Counter++;}
简而言之，我需要遍历帧并基于某些条件（实际上是最接近给定时间戳的条件）选择其中之一。
提前感谢。
英文:
Given some timestamp (probably second or ms precision), I need to exctract closest frame
in mp4 file with assumed camera timestamp(captured time, not pts or dts) for each frame, what is a more appropriate pipeline to exctract each frame within it's captured timestamp (smth like to use GetReferenceTimestampMeta from buffer)? Given that I work via gstreamer-sharp I expect to use appsink events, smth like:
private static void AppSink_NewSample(object o, NewSampleArgs args){if (o is AppSink aps){var sample = aps.PullSample();var buf = sample.Buffer;buf.Map(out var info, MapFlags.Read);//application/x-rtpvar tsMeta = buf.GetReferenceTimestampMeta();//NOTE tsMeta shouldn't be null there...//TODO some timestamps compare logicbuf.Unmap(info);}Counter++;}
Put it simple -- I need to iterate over frames and select one based on some condition (actually, closest to given timestamp).
Thanks in advance.
答案1
得分: 0
我找到了方法，它类似于：
var appSink = (AppSink)readerPipe.GetByName("my_appsink");readerPipe.SetName("frame_stepper");var q = readerPipe.SetState(State.Playing);var step = 1;while (step < frameNumber){appSink.PullSample();step++;}
英文:
I found the way, it is smth like:
var appSink = (AppSink) readerPipe.GetByName("my_appsink");readerPipe.SetName($"frame_stepper");var q = readerPipe.SetState(State.Playing);var step = 1;while (step < frameNumber){appSink.PullSample();step++;}
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